Utilising RO water

Published: 14 October, 2014

There have been many new technologies developed over the last half century to eliminate the need for open evaporative cooling but none of them have the efficiency that straight water-cooling can deliver. Andy Perkins sales manager, Kirton Engineering, reports.

There are the well-known down sides to using water cooling, not least is the need to be totally compliant to L8 and the upcoming HSG 274 plus any other relevant codes of practice.

Apart from the cost of scale and corrosion inhibitors and suitable biocidal control is the cost of water. Most cooling towers are controlled by bleeding off a certain proportion of water to ensure that there is no build-up of contaminants that cause a build-up of deposits or lead to corrosion of wetted areas.

pH control is necessary in cooling towers where a protective epoxy coating is present as too high a pH can lead to degradation of the coating and if the base metal is galvanised this can start to deteriorate.

Chlorides

Chlorides are also a particular area of concern in certain cooling towers as chloride attack of welds can take place in lower grade stainless steel fabricated systems. Very often total concentration factors and bleed rates are governed by this factor alone.

Using Reverse Osmosis (RO) water as part of the cooling tower make up water the total level of chlorides can be reduced to an acceptable level as well as reducing the pH of the overall make up water.

In order to for this to be cost effective the cost of producing the RO water (water, reject, salt and power) has to be low enough to allow the total cost benefit to be realised.

Very often factories have a total effluent discharge cap and as such any reduction in cooling tower bleed rates is very welcome and sometimes necessary.

By running an RO plant with a softened make up feed at 90% recovery rather than the traditional 75-80% it is possible to achieve water savings as well as increasing the total cycles of concentration in the cooling system and thus reducing the total volume of chemicals required.

Such systems are in operation based on a ratio of 50% RO water, 45% soft and 5% hard water.

Related Articles

The author Thomas Charlton was the first person to use the often misattributed phrase, "the price of liberty is eternal vigilance." Perhaps if he had he worked in the water treatment industry, he would have said, “the price of production is eternal vigilance.” Cooling towers are the perfect embodiment of this notion as they can accumulate a colossal 275kg of suspended matter in a single year if left untreated. This can lead to a range of issues that can negatively impact everything from efficiency to productivity, explains Simona Vasilescu, marketing manager of NCH Europe’s Water Treatment Innovation Platform.

A 200 tonne cooling tower can accumulate in excess of 275 Kg of suspended matter over the course of just one year. Allowing a cooling system to get weighed down by bacterial growth and slime build-up leaves it vulnerable to corrosion and fouling and is not worth the risk to plant operation. But do you know the enemy well enough to effectively keep microbial growth at bay?

With ever increasing sustainability, regulatory and financial pressures, VEOLIA WATER TECHNOLOGIES says now is the time to Rethink Water with its help. The company says Circular Economy initiatives operated by WRAP (Waste and Resources Action Programme) have achieved water reductions in many industries so what more can be done in 2017? Veolia says rethinking water can open up a wide range of opportunities to manage water more efficiently, reduce consumption and save money via water reuse or reduced discharge costs.

The UK’s high energy costs continue to present a major obstacle hindering the country’s manufacturing performance. A 2014 survey by the EEF highlighted the cost of energy as a major concern for UK manufacturers, with many identifying it a key factor impacting on their profitability and competitiveness. On sites where steam and hot water is used, significant cost savings can often be found in the boilerhouse and steam distribution system. Alan Hunt of ABB Measurement & Analytics offers advice on the best ways to optimise the efficiency of your steam boilers.